Too Much Training Can Tax Athletes' Brains (Short NPR Article)

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The note about decreased activty in the brain for decision-making lines up with what Steve Magness covered in his book ‘Peak Performance’. He notes that throughout the day your body essenetially has a specific volume or capacity of willpower and the more it’s used throughout the day, the harder it gets over time. Obviously it’s not saying that each day you have ‘X’ number of minutes of decision-making but I imagine it’s somewhat relative to the individual and then impacted by the training load. He also noted it’s why many people have a hard time sticking to very restrictive diets and will end up “cheating” at night because they pretty much hit that cap of willpower.

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This has been known for many years now – decision capacity. I forget which brain chem is responsible but yes, it’s limited in quantity. That’s the power of having routines and schedules etc, so we aren’t wasting valuable mental resources making inconsequential decisions (e.g. meals, workout). Applicable to everyone with a brain.


Sure. I think sometimes it falls to the wayside or isn’t realized by many athletes because the decisions made during training aren’t necessarily as distinct as other day-to-day choices. Something like going to the refridgerator and deciding on a snack is a very distinct moment in time whereas deciding if you can pedal harder in the middle of an interval is somewhat less conscious.

It could just as well be the opposite. Going to the fridge to snack may be an unconscious habit which has no intrinsic resource-wasting decision, whereas deciding to pedal harder…one has to overcome the body/brain’s innate homeostasis of being at rest/avoiding pain with a rather lengthy chain of strong decisions.

We know the brain is largely fueled by glucose, and this study highlights that acts of self-control use a relatively large amount of glucose. Racing and hard exercise also chew through your glucose, so… suddenly you don’t have the willpower to choose long-term rewards anymore.

Of course, it’s also possible to eventually get the brain to fuel via ketones instead of glucose. I don’t mean to ignore that circumstance, but going into ketosis (not just “eating low carb”) seems like a more extreme approach to the “problem” of the brain relying on glucose. Still, in some extreme cases, it might be worth considering (in conjunction with your doctor):

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That is interesting. I haven’t read more than your post yet, but it makes immediate sense to me. I guess the same happens the other way round, mental fatigue affects training.